PXD10RM Datasheet, PDF (821/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

22.5.9.1 LCD Reference Clock Select
Using LCDRCS the LCD reference clock can be selected. If LCDRCS is cleared, the system clock is
applied as reference clock to the prescaler input. If LCDRCS is set, the source clock for LCD Driver
system (prescaler input) is OSC clock. See device level documentation for detail on OSC clk. Selecting
the lower power consuming clock of both as reference clock for the prescaler input can save power
consumption.
22.5.9.2 Boost at Switching
Since the LCD appears like a capacitance to the driver it is sometimes useful to boost the output current
during transitions to increase the slew rate of the driver. If boosting is enabled, the drive strength capability
is increased a little ahead in time when the planes are switching, and reduced again to normal drive after
a certain time. To enable the boosting BSTEN need to be set. If BSTEN is not set, standard drive strength
is used.
Using the BST bit if BSTEN is set, LCD output current magnification (boost) can be selected. Available
is 8 times boosting, when BST is deasserted and 16 times boosting when BST is asserted.
The selected boost via BST bit can be switched to be always on by setting BSTAO, if BSTEN is set.
22.5.9.3 Standard Drive Selection
The output current has a direct impact on the power consumption and drive capability of the LCD64F6B
module. The PWR bits select the output current height and can be used to influence power consumption
and drive strength. Table 22-30 lists the possible selections of PWR.
Table 22-30. Output Current Selection (PWR)
PWR
Current
00
Standard Current
01
2 * Standard Current
10
3 * Standard Current
11
4 * Standard Current
22.5.9.4 Usage Recommendation
It is recommended to start with maximum output current and maximum enabled boosting. As long as the
LCD is fully functional in all environments a reduction of Output Current and boosting can be done.
When reducing the Output Current (PWR), the power consumption of the LCD module and the maximum
switching current of the planes is reduced.
When reducing or disabling the boosting (BST,BSTEN), the output current, while planes are switching, is
reduced.
The user can select any combination of PWR, BST, BSTEN, BSTAO to what fit his needs best.
Figure 22-24 gives an overview what is the impact when taking advance of Boost at Switching and
Standard Drive Selection.
Freescale Semiconductor
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
22-35